Technology Spotlight: GeoSierra Trenchless Permeable Reactive Barrier (PRB)
Cascade’s GeoSierra Trenchless Permeable Reactive Barrier (PRB) technology offers a unique approach to subsurface plume control and treatment by creating continuous, highly conductive reactive zones, without the disruption and limitations of traditional trenching. The system forms a vertical seam of pure reactive amendment, such as zero-valent iron, by inducing controlled subsurface fractures. Adjacent wells open to atmosphere are used to relieve pore pressure, ensuring the fracture propagates in the desired orientation. This method avoids the “mixed-in” amendment dilution seen in other injection-based PRBs and results in a uniform, permeable treatment zone that promotes groundwater flow directly through the barrier.
A biodegradable enzyme-based gel temporarily suspends the amendment during placement, then naturally breaks down to water and sugar, leaving behind a continuous, high-porosity seam of reactive media. The specialized expansion casings used to install the PRB allow for virtually unlimited depth, careful utility avoidance, and minimal surface disturbance. The casings can also remain in place for replenishment, biopolishing, or future injections.
This versatility makes the GeoSierra Trenchless PRB well-suited for addressing PFAS and other emerging contaminants, as well as sites with mixed contaminant plumes. PRBs can be strategically positioned for boundary control, mid-plume treatment, or source zone containment, and are often integrated into broader treatment trains.
Real-time resistivity imaging, carrier gel quality testing, and hydraulic characterization ensure proper installation and long-term performance. When combined with Cascade’s full suite of remediation technologies, the Trenchless PRB delivers a powerful, site-specific solution for complex contaminated sites.
